The dominant commercial method for producing phenol and acetone is by air oxidation of cumene to cumene hydroperoxide (CHP), followed by acid catalyzed decomposition of the CHP very selectively to phenol and acetone. Dimethylbenzyl alcohol (DMBA) is formed as the principle side product in the oxidation step and is subsequently dehydrated to alpha-methyl styrene (AMS) in the same acid catalyzed decomposition step. AMS is used commercially in the manufacture of plasticizers, resins and other polymers.
A variety of ways to purify the components of the crude product formed from acid catalyzed decomposition of cumene hydroperoxide mixtures are known. Most commercial processes utilize a two step, continuous flow approach to optimize overall yield in this step, especially of DMBA to AMS. Detailed descriptions of this process are disclosed in, e.g., U.S. Pat. Nos. 7,482,493; 7,109,385; 6,307,112; 6,225,513; 6,201,157; 6,057,483; 5,998,677; 5,463,136; 5,430,200; 5,371,305; 5,254,751; 5,064,507; 4,851,086; 4,634,796; and 4,358,618, each of which are incorporated herein by reference in their entirety. In another method, phenol and heavy components are separated from the rest of the mixture, which contains AMS, in a single distillation step.
In both approaches there is a stream, or location in a column, where AMS and phenol concentrate in the presence of organic acids resulting in the formation of undesirable heavy compounds which are lower value by-products that generally require further processing. In addition, these organic acids, such as formic acid and acetic acid, can generate a corrosive environment. Examples of heavy compounds include but are not limited to ortho- and para-cumyl phenol and dimers of AMS.